Highly efficient, one-step macrocyclizations assisted by the folding and preorganization of precursor oligomers

Highly efficient, one-step macrocyclizations leading to the formation of macrocyclic hexa(aramides) in high yields (69-82%) are described. The one-step macrocyclizations were facilitated by the preorganization or folding of the backbones of uncyclized precursors in the course of macrocyclization. The preorganization of backbones was achieved by the presence of localized three-centered hydrogen bonds that were adopted in the design of a class of closely related, backbone-rigidified foldamers. The macrocyclization involved reactions between diacid chloride 1 and diamine 2. The crude reaction mixtures and products were conveniently examined by mass spectrometric method (MALDI-TOF). Compared to most traditional one-step macrocyclizations that usually require high dilution conditions and often lead to very low overall yields of the desired products, cyclic hexamers 3 were obtained as the overwhelmingly major product under a variety of reaction conditions, suggesting the generality of this approach.     

Decarboxylative aldol reactions of allyl beta-keto esters via heterobimetallic catalysis

Mild and selective heterobimetallic-catalyzed decarboxylative aldol reactions involving allyl beta-keto esters have been developed. The reaction is promoted by Pd(0)- and Yb(III)-DIOP complexes at room temperature and involves the in situ formation of a ketone enolate from allyl beta-keto esters followed by addition of the enolate to aldehydes. The reaction is a new example of heterobimetallic catalysis in which the optimized reaction conditions require the addition of both metals.     

Storage-Reduction of NOx over Combined Catalysts of Pt/Ba/Al2O3-Mn/Ba/Al2O3： Carbon Monoxide as Reductant

Storage-reduction of NOx by carbon monoxide was investigated over combined catalysts of Mn/Ba/Al2O3-Pt/Ba/Al2O3. Combination of Mn/Ba/Al2O3 and Pt/Ba/Al2O3 catalysts in different ways showed excellent NOx storage-reduction performance and the content of Pt could be reduced by 50%. Not only the addition of 5Mn/15Ba/Al2O3 to lPt/15Ba/Al2O3 could improve its storage ability, but also enhance the NOx conversion consequently. NOx conversion over the combined catalysts (the combined catalysts I and II) was increased under dynamic lean-rich burn conditions, the maximum NOx conversion increased from 69.4% to respectively 78.8% and 75.7% over two combined catalysts.     

作为细胞微载体的明胶基缓释微球的制备

用改良的乳化冷凝法制备载牛血清蛋白(BSA)的大粒径明胶微球. 结果表明, 明胶水溶液的质量分数为25%、水相与油相体积比3∶20、搅拌速度300 r/min、交联剂用0.1 mL质量分数为25%的戊二醛、 表面活性剂用0.1 g span-80为制备平均直径约250 μm明胶微球的理想条件. 所制备微球的后处理方法不同, 则明胶微球的表面形貌也不同, 细胞粘附率不同. 空白明胶微球在体外可以完全降解, 载BSA的明胶微球对BSA具有良好的缓释性, 释放时间可长达30 d. 显微镜观察成纤维细胞在明胶微载体上生长良好.     

汽油族组成的近红外光谱快速测定

以荧光指示剂吸附色谱法（FIA）测定汽油族组成结果为基础，采用近红外光谱和化学计量学方法建立了快速、准确测定催化裂化馏出口汽油族组成（饱和烃、烯烃和芳烃）的分析模型；试验表明，该法分析速度快、重复性好、成本低，特别适用于生产中间控制分析。     

Membrane oscillator as chemical sensor

A rhythmic, sustained, stable potential oscillation was reproducibly observed for a lipid membrane supported by a micropore of a thin membrane tip micropipet. Amplitude and period of the oscillation voltage were controlled by changing the pore diameter. The smaller the hole diameter, the smaller the amplitude and the period became. We call this relationship “size effect.” We observed with an optical microscope dynamic behavior of lipids across the oil/water interface, which are formed at a micropore of 2 μm in diameter during self-excited potential oscillation. Periodical movement of a dome-shaped body on the interface is observed, and its expansion and shrinkage are quite synchronous with the potential oscillation. We also applied this self-excited potential oscillation device as a chemical sensor, and reported the effect of chemical substance added into the water phase as a model for the biological chemoreceptive membrane. The experimental results of microscopic observation show that the sensing system using the micropore can distinguish different chemical substances as well as their concentrations, suggesting its application as a chemical sensor.     

转动分辨的NH3X→C′→Ã跃迁的离子凹陷光谱

NH_3Ã(~1A_2~″)是一个快速预解离态, 以往的光谱研究从未得到它的转动分辨光谱。我们用两个脉冲染料激光器研究了NH_3C′→X的3+1多光子电离光谱和NH_3X→C′→Ã的折叠光学双共振多光子电离光谱, 称为“离子凹陷光谱”。对前者观察到了较高分辨的转动光谱, 得出C′v_2~′=O的高精度转动常数。通过谱线宽度, 得到了C′v_2~′=0,1,2能级的预解离寿命。从离子凹陷光谱上, 首次观察到了C′→Ã跃迁的0-0, 1-1, 2-2等带的转动分辨光谱。由双共振选择定则简化的光谱使漫散至～50 cm~(-1)线宽的转动线得以分开, 由此得到Ãv_2~″=0,1,2能级的转动常数和各谱带的带原点。在消除功率加宽的情况下, 测出Ãv_2~′=1能级的寿命。这种方法对研究分子的快速预解离态有一定的普遍意义。     

一氧化碳的双共振多光子电离研究

用两束脉冲染料激光进行了CO的光学双共振四光子电离, 获得了转动分辩的CO A~(1Π)←X~(1Σ~+)和B~(1Σ~+)←A~(1Π)跃迁的光谱。观察到了在此2+1光子相继吸收中特有的选择定则。动力学研究表明CO基态到A~(1Π)态的双光子吸收是速率决定步骤, 其吸收截面约为1×10~(-49) cm~4 s。还测定了A~(1Π)态的单态转动传能截面。对于宇称指数e守恒、△J×±1的过程的截面约为0.05 nm; 随△J值增大而减小。对相同的△J, e正负变号的过程的截面总是小于e不变过程的截面。     

An Overview of Molecular Packing Mode in Two‐Dimensional Organic Nanomaterials via Supramolecular Assembly

Two‐dimensional (2D) organic nanomaterials are attracting increasing research interest and expected to be the ideal candidate for future‐ proofed flexible electronics and biotechnologies. Owing to the complex molecular structures and multiple intermolecular interactions in organic systems, deeper understanding of rational molecular design and assembly principles is urgently required. In this review, a collection of molecular packing mode in the 2D organic nanomaterials via supramolecular assembly is presented, so as to help explicit the relationship among molecular structures, supramolecular interactions and molecular packing motifs in 2D assembly systems. We also provide a rational and accessible schematic model to demonstrate several typical kinds of molecular packing motifs for the prediction of the 2D morphology.     

中药微量元素含量区间尺最佳分级问题的探讨

在深入研究中药微量元素含量区间尺的基础上，从统计学角度对区间尺的最佳分级问题作了详细探讨，提出用5级区间尺来衡量中药中不同元素含量间相对高低水平，理论上更合理。